Polyurethanes represent a main class of synthetic elastomers applied for long-term, medical implants as they present tunable chemical properties, excellent mechanical properties, good blood compatibility, and also can be designed to degrade in biological environments [A. Rechichi et al., J. Biomed. Mater. Res., 84-A, 847 (2008)]. More specifically, polyether-urethane (PEU) and polyether-urethane-urea (PEUU) elastomers have long been considered ideal for use in many implanted devices, in spite of occasionally cited drawbacks [M. A. Schubert et al., J. Biomed. Mater. Res., 35, 319 (1997); B. Ward et al., J. Biomed. Mater. Res., 77-A, 380 (2008)]. Of the cited drawbacks are those associated with (1) the generation of aromatic diamines, which are considered to be toxic upon degradation of segmented copolymers made using aromatic diisocyanates for interlinking; (2) chain degradation due to oxidation or radiation degradation of the polyether component of segmented copolymers, and particularly those which encounter frequent mechanical stresses in the biological environment; and (3) chemical degradation in chemically and mechanically hostile biological environments of the urethane links of segmented copolymers and particularly those comprising reactive aromatic urethane linkages.
Liquid solventless, complex polymeric compositions, which thermoset at ambient temperatures through additional polymerization of a two-component system, wherein the first component comprises amine or acrylate-terminated polyurethanes or polyurethane-ureas and the second component comprises di- or polyacrylates have been described in U.S. Pat. No. 4,742,147. However, the prior art is virtually silent on self-standing PEU and PEUU liquid solventless compositions for use in pharmaceutical formulations and/or medical devices. Similarly, the prior art on polyether-urethanes is practically silent on hydroswellable (or water-swellable) systems, in spite of the fact that it covered elastomeric, segmented, hydrophilic polyether-urethane-based, lubricious coating compositions based on aromatic diisocyanate and polyethylene glycol (U.S. Pat. No. 4,990,357)—it did not suggest a self-standing material for medical device applications.
Collective analysis of the prior art on PEU and PEUU as discussed above regarding the drawbacks of the disclosed systems, absence of self-standing liquid and hydroswellable copolymers, and recognition of the need for new materials exhibiting properties that cannot be met by those of the prior art, provided a strong incentive to explore the synthesis and evaluation of the PEU and PEUU systems subject of this invention, which are structurally tailored for their effective use in existing and new applications.